Just passing through.

A 54-year-old man presented to his primary care physician with a 6-foot-long tapeworm in a jar after noting the specimen in a bowel movement the previous day. For several days prior to passing the worm, he had loose, non-bloody stools without abdominal pain or nausea. His past medical history was remarkable for a remote beef tapeworm infection. He denied travel, but regularly dined on sushi at various San Francisco restaurants several times a week.

Diphyllobothrium latum, the largest type of tapeworm, is associated with eating raw or undercooked freshwater fish. Sushi is not typically prepared with freshwater fish, but other preparations of freshwater fish, including gefilte fish and smoked fish, have been associated with D. latum infection. Infected patients usually remain asymptomatic for years, becoming aware of infection after passing segments in stool, as with this patient. Non-specific symptoms, obstructive symptoms or B12 deficiency can also occur. Diagnosis in this case was based on clinical history and identification of characteristic proglottids, linked segments containing central darker uterine stalks (see above). Identifying D. latum eggs in stool could also confirm the diagnosis. The patient was treated with one dose of praziquantel. Cure rates with single-dose therapy are approximately 85–93%1.